In a semiconductor device manufacturing process, a cassette or a transport container (carrier) called a FOUP (Front Opening Unified Pod), which accommodates a plurality of semiconductor wafers in multiple stages, is used. The carrier includes a body and an opening/closing door detachably attached to an opening portion of the body. Grooves for supporting semiconductor wafers are formed on the inner wall surface of the body of the carrier at a specified interval. The semiconductor wafers can be inserted into the grooves.
In order to determine the existence or absence and the position of semiconductor wafers accommodated within the carrier in multiple stages, a mapping process is performed in a state in which the carrier is mounted to a load port of a substrate processing system. Typically, an optical sensor including a light source and a light receiving unit is used in the mapping. To improve a sensor mechanism for the mapping process, for example, Patent Document 1 (Japanese Patent Laid-open Publication No. 2002-164411) proposes a FOUP opener in which a sensor advancing/retreating mechanism and a sensor attachment member are installed in a port door lift mechanism for opening and closing an opening/closing door of a FOUP.
If it is detected by the mapping process that a semiconductor wafer is deviated in position and accommodated in an abnormal state such as a tilted state, a conventional substrate processing system issues a warning and stops a process in a loader module that performs the carry-in and carry-out of semiconductor wafers using a FOUP. An operator manually conducts a correction work. The correction work is manually performed and is, therefore, time-consuming Thus, the correction work becomes a major culprit in prolonging the apparatus stop time and consequently reducing the productivity of the substrate processing system as a whole.
In order to correct the position of a semiconductor wafer within a carrier, for example, Patent Document 2 (Japanese Patent Laid-open Publication No. 2008-311419) proposes a technology in which a movable member protruding and retracting with respect to a mounting surface of a table is installed in a load port device provided with the table for mounting a carrier thereon and in which the position of a semiconductor wafer within the carrier is corrected by the vibration of the movable member. For the similar purpose, Patent Document 3 (Japanese Patent Laid-open Publication No. H11-204612) proposes the installation of a wafer position correction means which corrects the position of a semiconductor wafer by pressing the end surface of the semiconductor wafer accommodated within a cassette in a protruding state or the installation of a tilt drive means which tilts a cassette stage.
The proposals of Patent Documents 2 and 3 suffer from a problem of reduced usefulness because dedicated complex mechanisms should be additionally installed in a loader module in order to correct the position of a semiconductor wafer within a carrier.